Process for the hydrotreating of heavy hydrocarbon streams

ABSTRACT

The process comprises contacting a heavy hydrocarbon stream under suitable conditions and in the presence of hydrogen with a catalyst comprising a hydrogenating component selected from the group consisting of (1) molybdenum, chromium, and a small amount of cobalt, (2) their oxides, (3) their sulfides, and (4) mixtures thereof deposed on a large-pore, catalytically active alumina. The molybdenum is present in an amount within the range of about 5 wt.% to about 15 wt.%, calculated as MoO 3  and based upon total catalyst weight, the chromium is present in an amount within the range of about 5 wt.% to about 20 wt.%, calculated as Cr 2  O 3  and based upon the total catalyst weight, and the cobalt is present in an amount within the range of about 0.1 wt.% to about 5 wt.%, calculated as CoO and based upon the total catalyst weight. The catalyst possesses a pore volume within the range of about 0.4 cc/gm to about 0.8 cc/gm, a surface area within the range of about 150 m 2  /gm to about 300 m 2  /gm, and an average pore diameter within the range of about 100 A to about 200 A.

This application is a continuation-in-part application of copendingapplication U.S. Ser. No. 862,847, which was filed in the United StatesPatent and Trademark Office on Dec. 21, 1977, now abandoned.

CROSS REFERENCES TO RELATED APPLICATIONS

Two applications are being filed concurrently with this application. Thefirst of these, U.S. Ser. No. 967,432, is directed broadly to a processfor hydrotreating a heavy hydrocarbon stream containing metals,asphaltenes, nitrogen compounds, and sulfur compounds, which processemploys a catalyst comprising a hydrogenating component consistingessentially of a member selected from the group consisting of (1)molybdenum and chromium, (2) their oxides, (3) their sulfides, and (4)mixtures thereof on a suitable large-pore, catalytically active alumina.The second concurrently-filed application, U.S. Ser. No. 967,416, isdirected to a process for the cracking of a heavy hydrocarbon streamcontaining metals and asphaltenes wherein the stream is firsthydrotreated in the presence of a catalyst comprising a hydrogenatingcomponent comprising molybdenum and chromium, and optionally cobalt, ona large-pore alumina to produce a hydrotreated effluent and at least aportion of said hydrotreated effluent is then catalytically cracked.

BACKGROUND OF THE INVENTION

This invention is related to the catalytic treatment in the presence ofhydrogen of heavy hydrocarbon streams containing asphaltenic material,metals, nitrogen compounds, and sulfur compounds.

It is widely known that various organometallic compounds and asphaltenesare present in petroleum crude oils and other heavy petroleumhydrocarbon streams, such as petroleum hydrocarbon residua, hydrocarbonstreams derived from tar sands, and hydrocarbon streams derived fromcoal. The most common metals found in such hydrocarbon streams arenickel, vanadium, and iron. Such metals are very harmful to variouspetroleum refining operations, such as hydrocracking,hydrodesulfurization, and catalytic cracking. The metals and asphaltenescause interstitial plugging of the catalyst bed and reduced catalystlife.

The various metal deposits on a catalyst tend to poison or deactivatethe catalyst. Moreover, the asphaltenes tend to reduce thesusceptibility of the hydrocarbons to desulfurization. If a catalyst,such as a desulfurization catalyst or a fluidized cracking catalyst, isexposed to a hydrocarbon fraction that contains metals and asphaltenes,the catalyst will become deactivated rapidly and will be subject topremature removal from the particular reactor and replacement by newcatalyst.

Although processes for the hydrotreating of heavy hydrocarbon streams,including but not limited to heavy crudes, reduced crudes, and petroleumhydrocarbon residua, are known, the use of fixed-bed catalytic processesto convert such feedstocks without appreciable asphaltene precipitationand reactor plugging and with effective removal of metals and othercontaminants, such as sulfur compounds and nitrogen compounds, are nottoo common. While the heavy portions of hydrocarbon streams once couldbe used as a low-quality fuel or as a source of asphaltic-typematerials, the politics and economics of today require that suchmaterial be hydrotreated to remove environmental hazards therefrom andto obtain a greater proportion of usable products from such feeds.

It is well known that petroleum hydrocarbon streams can be hydrotreated,i.e., hydrodesulfurized, hydrodenitrogenated, and/or hydrocracked, inthe presence of a catalyst comprising a hydrogenating component and asuitable support material, such as an alumina, an alumina-silica, orsilica-alumina. The hydrogenating component comprises one or more metalsfrom Group VI and/or Group VIII of the Periodic Table of Elements, suchas the Periodic Table presented on page 628 of WEBSTER'S SEVENTH NEWCOLLEGIATE DICTIONARY, G. & C. Merriam Company, Springfield, Mass.,U.S.A. (1963). Such combinations of metals as cobalt and molybdenum,nickel and molybdenum, cobalt, nickel, and molybdenum, and nickel andtungsten have been found useful. For example, U.S. Pat. No. 3,340,180teaches that heavy hydrocarbon streams containing sulfur, asphalticmaterials, and metalliferous compounds as contaminants can behydrotreated in the presence of a catalyst comprising such metalcombinations and an activated alumina having less than 5% of its porevolume that is in the form of pores having a radius of 0 Angstrom units(A) to 300 A in pores larger than 100 A radius and having less than 10%of said pore volume in pores larger than 80 A radius.

U.S. Pat. No. 4,016,067 discloses that heavy hydrocarbon streams can bedemetalated and desulfurized in a dual catalyst system in which thefirst catalyst comprises a Group VI metal and a Group VIII metal,preferably molybdenum and cobalt, composited with an alumina supporthaving a demonstratable content of delta-alumina and/or theta-aluminaand has at least 60% of its pore volume in pores having a diameter ofabout 100 A to 200 A, at least about 5% of its pore volume in poresgreater than 500 A in diameter, and a surface area of up to about 110square meters per gram (m² /gm) and in which the second catalystcomprises a similar hydrogenating component composited with a refractorybase, preferably alumina, and has at least 50%, and preferably at least60%, of its pore volume contributed by pores that have a diameter of 30A to 100 A and a surface area of at least 150 m² /gm.

U.S. Pat. No. 2,890,162 teaches that catalysts comprising activecatalytic components on alumina and having a most frequent pore diameterof 60 A to 400 A and pores which may have diameters in excess of 1,000 Aare suitable for desulfurization, hydrocracking, hydroforming ofnaphthene hydrocarbons, alkylation, reforming of naphthas, isomerizationof paraffins and the like, hydrogenation, dehydrogenation, and varioustypes of hydrofining operations, and hydrocracking of residua and otherasphalt-containing materials. It is suggested that suitable activecomponents and promoters comprise a metal or a catalytic compound ofvarious metals, molybdenum and chromium being among 35 listed metals.

United Kingdom Patent Specification No. 1,051,341 discloses a processfor the hydrodealkylation of certain aromatics, which process employs acatalyst consisting of the oxides or sulfides of a Group VI metalsupported on alumina, having a porosity of 0.5 milliliters per gram(ml/gm) to 1.8 ml/gm and a surface area of 138 m² /gm to 200 m² /gm, atleast 85% of the total porosity being due to pores having a diameter of150 A to 550 A.

U.S. Pat. Nos. 3,245,919 and 3,267,025 disclose hydrocarbon conversionprocesses, such as reforming, hydrocracking, hydrodesulfurization,isomerization, hydrogenation, and dehydrogenation, that employ acatalyst of a catalytic amount of a metal component selected from metalsof Group VI and Group VIII, such as chromium, molybdenum, tungsten,iron, nickel, cobalt, and the platinum group metals, their compounds,and mixtures thereof, supported on gamma-alumina obtained by the dryingand calcining of a boehmite alumina product and having a pore structuretotalling at least about 0.5 cc/gm in pores larger than 80 A in size.

U.S. Pat. No. 3,630,888 teaches the treatment of residuum hydrocarbonfeeds in the presence of a catalyst comprising a promoter selected fromthe group consisting of the elements of Group VIB and Group VIII of thePeriodic Table, oxides thereof, and combinations thereof, and aparticulate catalytic agent of silica, alumina, and combinationsthereof, having a total pore volume greater than 0.40 cubic centimetersper gram (cc/gm), which pore volume comprises micropores and accesschannels, the access channels being interstitially spaced through thestructure of the micropores, a first portion of the access channelshaving diameters between about 100 A and about 1,000 A, which firstportion comprises 10% to 40% of the pore volume, a second portion of theaccess channels having diameters greater than 1,000 A, which secondportion comprises 10% to 40% of the pore volume, and the remainder ofthe pore volume being micropores having diameters of less than 100 A,which remainder comprises 20% to 80% of the total pore volume.

U.S. Pat. No. 3,114,701, while pointing out that in hydrofiningprocesses nitrogen compounds are removed from petroleum hydrocarbons inthe presence of various catalysts generally comprising chromium and/ormolybdenum oxides together with iron, cobalt, and/or nickel oxides on aporous oxide support, such as alumina or silica-alumina, discloses ahydrodenitrification process employing a catalyst containing largeconcentrations of nickel and molybdenum on a predominantly aluminacarrier to treat hydrocarbon streams boiling at 180° F. to about 1,050°F.

U.S. Pat. No. 2,843,552 discloses that a catalyst containing chromia inan appreciable amount with alumina provides a very good attritionresistant catalyst, can have molybdenum oxide impregnated thereon, andcan be used in reforming, desulfurization, and isomerization processes.

U.S. Pat. No. 2,577,823 teaches that hydrodesulfurization of heavyhydrocarbon fractions containing from 1% to 6.5% sulfur in the form oforganic sulfur compounds, such as a reduced crude, can be conducted overa catalyst of chromium, molybdenum, and aluminum oxides, which catalystis prepared by simultaneously precipitating the oxides of chromium andmolybdenum on a preformed alumina slurry at a pH of 6 to 8.

U.S. Pat. No. 3,265,615 discloses a method for preparing a supportedcatalyst in which a catalyst carrier of high surface area, such asalumina, is impregnated with ammonium molybdate and then immersed in anaqueous solution of chromic sulfate, and the treated carrier is driedovernight and subsequently reduced by treatment with hydrogen at thefollowing sequential temperatures: 550° F. for 1/2 hour; 750° F. for 1/2hour; and 950° F. for 1/2 hour. The reduced material is sulfided andemployed to hydrofine a heavy gas oil boiling from 650° F. to 930° F.

U.S. Pat. No. 3,956,105 discloses a process for hydrotreating petroleumhydrocarbon fractions, such as residual fuel oils, which process employsa catalyst comprising a Group VIB metal (chromium, molybdenum,tungsten), a Group VIII metal (nickel, cobalt) and a refractoryinorganic oxide, which can be alumina, silica, zirconia, thoria, boria,chromia, magnesia, and composites thereof. The catalyst is prepared bydry mixing a finely divided Group VIB metal compound, a Group VIII metalcompound, and a refractory inorganic oxide, peptizing the mixture andforming an extrudable dough, extruding, and calcining.

U.S. Pat. No. 3,640,817 discloses a two-stage process for treatingasphaltene-containing hydrocarbons. Both catalysts in the processcomprise one or more metallic components selected from the groupconsisting of molybdenum, tungsten, chromium, iron, cobalt, nickel, andthe platinum group metals on a porous carrier material, such as alumina,silica, zirconia, magnesia, titania, and mixtures thereof, the firstcatalyst having more than 50% its macropore volume characterized bypores having a pore diameter that is greater than about 1,000 A and thesecond catalyst having less than 50% of its macropore volumecharacterized by pores having a pore diameter that is greater than about1,000 A.

U.S. Pat. No. 3,957,622 teaches a two-stage hydroconversion process fortreating asphaltene-containing black oils. Desulfurization occurs in thefirst stage over a catalyst that has less than 50% of its macroporevolume characterized by pores having a pore diameter greater than about1,000 A. Accelerated conversion and desulfurization of the asphaltenicportion occur in the second stage over a catalyst having more than 50%of its macropore volume characterized by pores having a pore diameterthat is greater than 1,000 A. Each catalyst comprises one or moremetallic components selected from the group consisting of molybdenum,tungsten, chromium, iron, cobalt, nickel, the platinum group metals, andmixtures thereof on a support material of alumina, silica, zirconia,magnesia, titania, boria, strontia, hafnia, or mixtures thereof.

French patent publication No. 2,281,972 teaches the preparation of acatalyst comprising the oxides of cobalt, molybdenum, and/or nickel on abase of aluminum oxide and 3 to 15 wt. % chromium oxide and its use forthe refining of hydrocarbon fractions, preferably for thehydrodesulfurization of fuel oils obtained by vacuum distillation orresidual oils obtained by atmospheric distillation. The base can beprepared by co-precipitation of compounds of chromium and aluminum.

U.S. Pat. No. 3,162,596 teaches that, in an integrated process, aresidual hydrocarbon oil containing metal contaminants (nickel andvanadium) is first hydrogenated either with a hydrogen donor diluent orover a catalyst having one or more hydrogenation promoting metalssupported on a solid carrier exemplified by alumina or silica and thenvacuum distilled to separate a heavy gas oil fraction containing reducedquantities of metals from an undistilled residue boiling primarily aboveabout 1,100° F. and containing asphaltic material. The heavy gas oilfraction is subsequently catalytically cracked.

U.S. Pat. No. 3,180,820 discloses that a heavy hydrocarbon stock can beupgraded in a two-zone hydrodesulfurization process, wherein each zoneemploys a solid hydrogenation catalyst comprising one or more metalsfrom Groups VB, VIB, and VIII of the Periodic Table of Elements. Eithercatalyst can be supported or unsupported. In a preferred embodiment, thefirst zone contains an unsupported catalyst-oil slurry and the secondzone contains a supported catalyst in a fixed bed, slurry, or fluidizedbed. The support of the supported catalyst is a porous refractoryinorganic oxide carrier, including alumina, silica, zirconia, magnesia,titania, thoria, boria, strontia, hafnia, and complexes of two or moreoxides, such as silica-alumina, silica-zirconia, silica-magnesia,aluminatitania, and silica-magnesia-zirconia, among others. The patentprovides that the supported catalyst which is appropriate for use in theinvention will have a surface area of about 50 m² /gm to 700 m² /gm, apore diameter of about 20 A to 600 A, and a pore volume of about 0.10ml/gm to 20 ml/gm.

U.S. Pat. Nos. 3,977,961 and 3,985,684 disclose processes for thehydroconversion of heavy crudes and residua, which processes employ oneor two catalysts, each of which comprises a Group VIB metal and/or aGroup VIII metal on a refractory inorganic oxide, such as alumina,silica, zirconia, magnesia, boria, phosphate, titania, ceria, andthoria, can comprise a Group IVA metal, such as germanium, has a veryhigh surface area and contains ultra-high pore volume. The firstcatalyst has at least about 20% of its total pore volume of absolutediameter within the range of about 100 A to about 200 A, when thecatalyst has a particle size diameter ranging up to 1/50 inch, at leastabout 15% of its total pore volume of absolute diameter within the rangeof about 150 A to about 250 A, when the catalyst has a particle sizediameter ranging from about 1/50 inch to about 1/25 inch, at least about15% of its total pore volume of absolute diameter within the range ofabout 175 A to about 275 A, when the catalyst has an average particlesize diameter ranging from about 1/25 inch to about 1/8 inch, a surfacearea of about 200 m² /gm to about 600 m² /gm, and a pore volume of about0.8 cc/gm to about 3.0 cc/gm. The second catalyst has at least about 55%of its total pore volume of absolute diameter within the range of about100 A to about 200 A, less than 10% of its pore volume with porediameters of 50 A-, less than about 25% of its total pore volume withpore diameters of 300 A+, a surface area of about 200 m² /gm to about600 m² /gm, and a pore volume of about 0.6 cc/gm to about 1.5 cc/gm.These patents teach also that the effluent from such processes may besent to a catalytic cracking unit or a hydrocracking unit.

U.S. Pat. No. 4,054,508 discloses a process for demetallization anddesulfurization of residual oil fractions, which process utilizes 2catalysts in 3 zones. The oil is contacted in the first zone with amajor portion of a first catalyst comprising a Group VIB metal and aniron group metal oxide composited with an alumina support, the firstcatalyst having at least 60% of its pore volume in pores of 100 A to 200A diameter and at least about 5% of its pore volume in pores having adiameter greater than 500 A, in the second zone with the second catalystcomprising a Group VIB metal and an iron group metal oxide compositedwith an alumina support, the second catalyst having a surface area of atleast 150 m² /gm and at least 50% of its pore volume in pores withdiameters of 30 A to 100 A, and then in a third zone with a minorportion of the first catalyst.

Now there has been found and developed a process for hydrotreating aheavy hydrocarbon stream containing metals and asphaltenes, nitrogencompounds, and sulfur compounds, which process employs a catalyst thathas special physical characteristics and a hydrogenating componentcontaining cobalt, molybdenum, and chromium.

SUMMARY OF THE INVENTION

Broadly, according to the present invention, there is provided a processfor the hydrotreating of a heavy hydrocarbon stream containing metals,asphaltenes, nitrogen compounds, and sulfur compounds, which processcomprises contacting said stream under suitable conditions and in thepresence of hydrogen with a catalyst comprising a hydrogenatingcomponent selected from the group consisting of (1) molybdenum, chromiumand a small amount of cobalt, (2) their oxides, (3) their sulfides, and(4) mixtures thereof on a large-pore, catalytically active alumina, saidmolybdenum being present in an amount within the range of about 5 wt. %to about 15 wt. %, calculated as MoO₃ and based upon the total catalystweight, said chromium being present in an amount within the range ofabout 5 wt. % to about 20 wt. %, calculated as Cr₂ O₃ and based upon thetotal catalyst weight, said cobalt being present in an amount within therange of about 0.1 wt. % to about 5 wt. %, calculated as CoO and basedupon the total catalyst weight, and said catalyst possessing a porevolume within the range of about 0.4 cc/gm to about 0.8 cc/gm, a surfacearea within the range of about 150 m² /gm to about 300 m² /gm, and anaverage pore diameter within the range of about 100 A to about 200 A.

The catalyst that is employed in the process of the present inventionhas about 0% to about 10% of its pore volume in pores having diametersthat are smaller than 50 A, about 30% to about 80% of its pore volume inpores having diameters of about 50 A to about 100 A, about 10% to about50% of its pore volume in pores having diameters of about 100 A to about150 A, and about 0% to about 10% of its pore volume in pores havingdiameters that are larger than 150 A.

The catalyst that is employed in the process of the present invention isconveniently prepared by calcining the alumina (pseudo-boehmite) instatic air at a temperature of about 800° F. to about 1,400° F. for aperiod of time within the range of about 1/2 hour to about 2 hours toproduce a gamma-alumina and subsequently impregnating the gamma-aluminawith one or more aqueous solutions containing heat-decomposable salts ofthe cobalt, molybdenum, and chromium.

The process of the present invention is carried out at a hydrogenpartial pressure within the range of about 1,000 psia to about 3,000psia, an average catalyst bed temperature within the range of about 700°F. to about 820° F., a liquid hourly space velocity (LHSV) within therange of about 0.1 volume of hydrocarbon per hour per volume of catalystto about 3 volumes of hydrocarbon per hour per volume of catalyst, and ahydrogen recycle rate or hydrogen addition rate within the range ofabout 2,000 standard cubic feet of hydrogen per barrel of hydrocarbon(SCFB) to about 15,000 SCFB.

BRIEF DESCRIPTION OF THE DRAWING

The accompanying FIGURE is a simplified flow diagram of a preferredembodiment of the process of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a novel process for thehydrotreating of heavy hydrocarbon feedstocks. Such feedstocks willcontain asphaltenes, metals, nitrogen compounds, and sulfur compounds.It is to be understood that the feedstocks that are to be treated by theprocess of the present invention will contain from a small amount ofnickel and vanadium, e.g., less than 40 ppm, up to more than 1,000 ppmof nickel and vanadium (a combined total amount of nickel and vanadium)and up to about 25 wt.% asphaltenes. If the feedstock contains either acombined amount of nickel and vanadium that is too large or an amount ofasphaltenes that is exceptionally large, the feedstock can be subjectedto a preliminary treatment to reduce the excessive amount of theparticular contaminant. Such preliminary treatment will comprise asuitable hydrogenation treatment for the removal of metals from thefeedstock and/or the conversion of asphaltenes in the feedstock toreduce the contaminants to satisfactory levels, such treatment employingany suitable relatively cheap catalyst. The above-mentioned contaminantswill deleteriously affect the subsequent processing of such feedstocks,if they are not lowered to acceptable levels.

Typical feedstocks that can be treated satisfactory by the process ofthe present invention will often contain a substantial amount ofcomponents that boil appreciably above 1,000° F. Examples of typicalfeedstocks are crude oils, topped crude ois, petroleum hydrocarbonresidua, both atmospheric and vacuum residua, oils obtained from tarsands and residua derived from tar sand oil, and hydrocarbon streamsderived from coal. Such hydrocarbon streams contain organometalliccontaminants which create deleterious effects in various refiningprocesses that employ catalysts in the conversion of the particularhydrocarbon stream being treated. The metallic contaminants that arefound in such feedstocks include, but are not limited to, iron,vanadium, and nickel.

Nickel is present in the form of soluble organometallic compounds inmost crude oils and residuum fractions. The presence of nickel prophyrincomplexes and other nickel organometallic complexes causes severedifficulties in the refining and utilization of heavy hydrocarbonfractions, even if the concentration of such complexes is relativelysmall. It is known that a cracking catalyst deteriorates rapidly and isselectivity changes when in the presence of an appreciable quantity ofthe organometallic nickel compounds. An appreciable quantity of suchorganometallic nickel compounds in feedstocks that are beinghydrotreated or hydrocracked harmfully affects such processes. Thecatalyst becomes deactivated and plugging or increasing of the pressuredrop in a fixed-bed reactor results from the deposition of nickelcompounds in the interstices between catalyst particles.

Iron-containing compounds and vanadium-containing compounds are presentin practically all crude oils that are associated with the highConradson carbon asphaltic and/or asphaltenic portion of the crude. Ofcourse, such metals are concentrated in the residual bottoms, when acrude is topped to remove those fractions that boil below about 450° F.to 600° F. If such residuum is treated by additional processes, thepresence of such metals adversely affects the catalyst in suchprocesses. It should be pointed out that nickel-containing compoundsdeleteriously affect cracking catalysts to a greater extent than doiron-containing compounds. If an oil containing such metals is used as afuel, the metals will cause poor fuel oil performance in industrialfurnaces, since they corrode the metal surfaces of the furnaces.

While metallic contaminants, such as vanadium, nickel, and iron, areoften present in various hydrocarbon streams in rather small amounts,they are often found in concentrations in excess of 40 to 50 ppm byweight, often in excess of 1,000 ppm. Of course, other metals are alsopresent in a particular hydrocarbon stream. Such metals exist as theoxides or sulfides of the particular metal, or they are present as asoluble salt of the particular metal, or they are present as highmolecular weight organometallic compounds, including metal naphthenatesand metal porphyrins, and derivatives thereof. In any event, if themetals content of the feed stream is too large, the feed stream shouldbe treated for demetallization prior to use in the process of thepresent invention in order to appreciably reduce the metals to a morepractical level.

Broadly, according to the process of the present invention, there isprovided a process for hydrotreating a heavy hydrocarbon streamcontaining metals, asphaltenes, nitrogen compounds, and sulfurcompounds, which process comprises contacting said stream under suitableconditions and in the presence of hydrogen with a catalyst comprising ahydrogenating component selected from the group consisting of (1)molybdenum, chromium and a small amount of cobalt, (2) their oxides, (3)their sulfides, and (4) mixtures thereof on a large-pore, catalyticallyactive alumina, said molybdenum being present in an amount within therange of about 5 wt.% to about 15 wt.%, calculated as MoO₃ and basedupon the total catalyst weight, said chromium being present in an amountwithin the range of about 5 wt.% to about 20 wt.%, calculated as Cr₂ O₃and based upon the total catalyst weight, said cobalt being present inan amount within the range of about 0.1 wt.% to about 5 wt.%, calculatedas CoO and based upon the total catalyst weight, and said catalystpossessing a pore volume within the range of about 0.4 cc/gm to about0.8 cc/gm, a surface area within the range of about 150 m² /gm to about300 m² /gm, and an average pore diameter within the range of about 100 Ato about 200 A.

It is to be understood that as used herein all values that are given forsurface area would be those that are obtained by the BET nitrogenadsorption method; all values that are given for pore volume would bethose that are obtained by nitrogen adsorption; and all values that aregiven for average pore diameter would be those that are calculated bymeans of the expression: ##EQU1## wherein

A.P.D.=average pore diameter in A,

P.V.=pore volume in cc/gm, and

S.A.=surface area in m² /gm.

Furthermore, pore size distributions are those that are obtained by aDigisorb 2500 instrument through the use of nitrogen desorptiontechniques.

In the process of the present invention, the catalyst provides gooddemetallization activity, good desulfurization activity, good metalsremoval, good asphaltene conversion, and good conversion of the 1,000°F.+ material to 1,000° F.- material.

The hydrogenating component of the catalyst that is employed in theprocess of the present invention is made up of cobalt, molybdenum, andchromium. The cobalt, molybdenum, and chromium are present in theelemental form, as oxides of the metals, as sulfides of the metals, ormixtures thereof. The cobalt is present in an amount within the range ofabout 0.1 wt.% to about 5 wt.%, calculated as CoO and based upon thetotal catalyst weight. The molybdenum is present in an amount within therange of about 5 wt.% to about 15 wt.%, calculated as MoO₃ and basedupon the total catalyst weight. The chromium is present in an amountwithin the range of about 5 wt.% to about 20 wt.%, calculated as Cr₂ O₃and based upon the total catalyst weight. Preferably, the cobalt ispresent in an amount within the range of about 1 wt.% to about 3 wt.%,calculated as CoO and based upon the total catalyst weight, themolybdenum is present in an amount within the range of about 7 wt.% toabout 13 wt.%, calculated as MoO₃ and based upon the total catalystweight, and the chromium is present in an amount within the range ofabout 6 wt.% to about 15 wt.%, calculated as Cr₂ O₃ and based upon thetotal catalyst weight.

Suitable catalytically active large-pore aluminas are employed in thecatalyst that is utilized in the process of the present invention. Atypical example of such an alumina is Aero-100 alumina, manufactured bythe American Cyanamid Company. The alumina should have a pore volumethat is in excess of 0.4 cc/gm, a surface area that is in excess of 150m² /gm, and an average pore diameter that is greater than 100 A.

Typically, the catalytic composition that is employed in the process ofthe present invention may be prepared by impregnating the various metalsupon the suitable catalytically active large-pore alumina. Suchimpregnation may be accomplished with one or more solutions ofheat-decomposable compounds of the appropriate metals. The impregnationmay be a co-impregnation when a single solution of the metals isemployed. Alternatively, impregnation may be accomplished by thesequential impregnation of the various metals from two or more solutionsof the heat-decomposable compounds of the appropriate metals. Theimpregnated support is dried at a temperature of at least 250° F. for aperiod of at least 1 hour and calcined in air at a temperature of atleast 1,000° F. for a period of time of at least 2 hours. Preferably,the catalyst that is used in the process of the present invention isprepared by first calcining pseudo-boehmite in static air at atemperature of about 800° F. to about 1,400° F. for a period of timewithin the range of about 1/2 hour to about 2 hours to produce agamma-alumina. This gamma-alumina is subsequently impregnated with theaqueous solution or solutions containing the heat-decomposable salts ofthe cobalt, molybdenum, and chromium.

The finished catalyst that is employed in the process of the presentinvention possesses a pore volume within the range of about 0.4 cc/gm toabout 0.8 cc/gm, a surface area within the range of about 150 m² /gm toabout 300 m² /gm, and an average pore diameter within the range of about100 A to about 200 A. Preferably, the catalyst possesses a pore volumewithin the range of about 0.5 cc/gm to about 0.7 cc/gm, a surface areawithin the range of about 150 m² /gm to about 250 m² /gm, and an averagepore diameter within the range of about 110 A to about 150 A.

The catalyst employed in the process of the present invention shouldhave about 0% to about 10% of its pore volume in pores having diametersthat are smaller than 50 A, about 30% to about 80% of its pore volume inpores having diameters of about 50 A to about 100 A, about 10% to about50% of its pore volume in pores having diameters of about 100 A to about150 A, and about 0% to about 10% of its pore volume in pores havingpores that are larger than 150 A.

The process of the subject application is particularly useful forhydrotreating heavy hydrocarbon streams such as petroleum residua, bothatmospheric resids and vacuum resids, tar sands oils, tar sands resids,and liquids obtained from coal. In addition, the process may be employedto satisfactorily hydrotreat petroleum hydrocarbon distillates, such asgas oils, cycle stocks, and furnace oils. If the amount of nickel andvanadium is excessive or the concentration of asphaltenes is too large,the feedstock should be subjected to a preliminary treatment to reducethe excessive amount or amounts to more tolerable levels before thefeedstock is used in the process of the present invention.

Operating conditions for the hydrotreatment of heavy hydrocarbonstreams, such as petroleum hydrocarbon residua and the like, comprise ahydrogen partial pressure within the range of about 1,000 psia to about3,000 psia, an average catalyst bed temperature within the range ofabout 700° F. to about 820° F., a LHSV within the range of about 0.1volume of hydrocarbon per hour per volume of catalyst to about 3 volumesof hydrocarbon per hour per volume of catalyst, and a hydrogen recyclerate of hydrogen addition rate within the range of about 2,000 SCFB toabout 15,000 SCFB. Preferably, the operating conditions comprise ahydrogen partial pressure within the range of about 1,200 psia to about2,000 psia; an average catalyst bed temperature within the range ofabout 730° F. to about 810° F.; a LHSV within the range of about b 0.4to about 1; and a hydrogen recycle rate or hydrogen addition rate withinthe range of about 5,000 SCFB to about 10,000 SCFB.

If the process of the present invention were to be used to treathydrocarbon distillates, the operating conditions would comprise ahydrogen partial pressure within the range of about 200 psia to about3,000 psia; an average catalyst bed temperature within the range ofabout 600° F. to about 800° F.; a LHSV within the range of about 0.4volume of hydrocarbon per hour per volume of catalyst to about 6 volumesof hydrocarbon per hour per volume of catalyst; and a hydrogen recyclerate or hydrogen addition rate within the range of about 1,000 SCFB toabout 10,000 SCFB. Preferred operating conditions for the hydrotreatingof hydrocarbon distillates comprise a hydrogen partial pressure withinthe range of about 200 psia to about 1,200 psia; an average catalyst bedtemperature within the range of about 600° F. to about 750° F.; a LHSVwithin the range of about 0.5 volume of hydrocarbon per hour per volumeof catalyst to about 4 volumes of hydrocarbon per hour per volume ofcatalyst; and a hydrogen recycle rate or hydrogen addition rate withinthe range of about 1,000 SCFB to about 6,000 SCFB.

A preferred embodiment of the process of the present invention ispresented in the accompanying figure, which is a simplified flow diagramand does not show various pieces of auxiliary equipment, such as pumps,compressors, heat exchangers, and valves. Since one having ordinaryskill in the art would recognize easily the need for and location ofsuch auxiliary equipment, its omission is appropriate and facilitatesthe simplification of the figure. This process scheme is presented forthe purpose of illustration only and is not intended to limit the scopeof the present invention.

Referring to the figure, an Arabian light vacuum resid, containing about4 wt.% sulfur, less than 0.5 wt.% nitrogen, and less than 100 ppm ofnickel and vanadium, is withdrawn from source 10 through line 11 intopump 12, whereby it is pumped through line 13. A hydrogen-containingrecycle gas stream, discussed hereinafter, is passed from line 14 intoline 13 to be mixed with the hydrocarbon feed stream to form a mixedhydrogen-hydrocarbon stream. The mixed hydrogen-hydrocarbon stream isthen passed from line 13 into furnace 15 where it is heated to atemperature within the range of about 760° F. to about 780° F. Theheated stream is then passed through line 16 into reaction zone 17.

Reaction zone 17 comprises one or more reactors, each of which containsone or more fixed beds of catalyst. The catalyst comprises ahydrogenation component comprising about 0.1 wt.% to about 5 wt.%cobalt, calculated as CoO and based upon the total catalyst weight,about 5 wt.% to 15 wt.% molybdenum, calculated as MoO₃ and based uponthe total catalyst weight, and about 5 wt.% to about 20 wt.% chromium,calculated as Cr₂ O₃ and based upon the total catalyst weight, on alarge-pore, catalytically active alumina. The cobalt, molybdenum, andchromium are present either in the elemental form, as oxides of themetals, as sulfides of the metals, or as mixtures thereof. The catalysthas a pore volume within the range of about 0.4 cc/gm to about 0.8cc/gm, a surface area within the range of about 150 m² /gm to about 300m² /gm, an average pore diameter within the range of about 100 A toabout 200 A, and a pore-size distribution wherein about 0% to about 10%of the pore volume is in pores having diameters that are smaller that 50A, about 30% to about 80% of the pore volume is in pores havingdiameters within the range of about 50 A to about 100 A, about 10% toabout 50% of the pore volume is in pores having diameters within therange of about 100 A to about 150 A, and about 0% to about 10% of thepore volume is in pores having diameters that are larger then 150 A.

The operating conditions employed in this scheme comprise a hydrogenpartial pressure of about 1,200 psia to about 1,600 psia, an averagecatalyst bed temperature within the range of about 760° F. to about 780°F.; an LHSV within the range of about 0.4 volume of hydrocarbon per hourper volume of catalyst to about 0.8 volume of hydrocarbon per hour pervolume of catalyst; and a hydrogen recycle rate within the range ofabout 5,000 SCFB to about 8,000 SCFB.

The effluent from reaction zone 17 is passed through line 18 intohigh-temperature, high-pressure, gas-liquid separator 19, which isoperated at reactor pressure and a temperature within the range of about760° F. to about 780° F. In separator 19, hydrogen-containing gas isseparated from the rest of the effluent. The hydrogen-containing gas ispassed from separator 19 through line 20. It is cooled and sent intolight-hydrocarbon separator 21, wherein the condensed light hydrocarbonsare separated from the hydrogen-containing gas and withdrawn via line22. The hydrogen-containing gas is removed by way of line 23 and passedinto scrubber 24, wherein the hydrogen sulfide is removed or scrubbedfrom the gas. The hydrogen sulfide is removed from the system by way ofline 25. The scrubbed hydrogen-containing gas is then passed throughline 14 where it can be joined by make-up hydrogen, if necessary, vialine 26. The hydrogen-containing gas stream is then added to thehydrocarbon feed stream in line 13, as described hereinabove.

The liquid portion of the effluent is passed from the high-temperature,high-pressure, gas-liquid separator 19 by way of line 27 tohigh-temperature flash drum 28. In flash drum 28, the pressure isreduced to atmospheric pressure and the temperature of the material iswithin the range of about 700° F. to about 800° F. In flash drum 28, thelight hydrocarbons containing not only the naphtha but those distillatesboiling up to a temperature of about 550° F. to 600° F., such as fueloils, is flashed from the rest of the product and is removed from thesystem by way of line 29. Such light hydrocarbons, which comprise about1 wt.% to about 4 wt.% C₄ -material, about 2 wt.% to 5 wt.% naphtha (C₅to 360° F. material), and about 10 wt.% to about 15 wt.% 360° F.-650° F.material, based upon hydrocarbon feed, can be separated into theirvarious components and sent to storage or to other processing units.

The heavier material that is separated from the light hydrocarbons, thatis, material that boils at a temperature above about 600° F., present inan amount of about 60 wt.% to about 90 wt.% based upon the hydrocarbonfeed, is removed from flash drum 28 by way of line 30 for use as feedsto other processes or as a low-sulfur, heavy industrial fuel. Suchliquid material contains about 0.6 wt.% to about 1.2 wt.% sulfur, about1.0 wt.% to about 3.0 wt.% asphaltenes, and about 5 ppm to about 15 ppmnickel and vanadium. Furthermore, more than 50% of the 1,000°F.+material is converted to 1,000° F.-material.

This liquid effluent is passed via line 31 to furnace 32, or othersuitable heating means, to be heated to a temperature as high as 800°.

The heated stream from furnace 32 is passed by way of line 33 intovacuum tower 34, where vacuum gas oil (VGO) is separated from alow-sulfur residual fuel. The VGO is passed from vacuum tower 34 by wayof line 35 to storage or to a conventional catalytic cracking unit (notshown). The low-sulfur residual fuel is passed from vacuum tower 34 byway of line 36 to storage or to other processing units where it can beused as a source of energy.

Alternatively, the material boiling above 600° F. that is removed fromflash drum 28 through line 30 can be sent by way of line 37 to a residcatalytic cracking unit (not shown).

The following examples are presented to facilitate the understanding ofthe present invention and are presented for the purposes of illustrationonly and are not intended to limit the scope of the present invention.

EXAMPLE 1

A catalyst, hereinafter identified as Catalyst A, was prepared tocontain 1.1 wt.% CoO, 8.2 wt.% MoO₃, and 8.2 wt.% Cr₂ O₃, based upon thetotal catalyst weight, on a large-pore, catalytically active alumina. A63.8-gram sample of Aero-100 alumina, obtained from the AmericanCyanamid Company, was impregnated with a solution containing ammoniumdichromate and ammonium molbydate. The Aero-100 alumina was in the formof 14-to-20-mesh material and had been previously calcined at atemperature of about 1,200° F. in air for a period of 2 hours.

The solution that was used for the impregnation was prepared bydissolving 10.6 grams of ammonium dichromate and 8.3 grams of ammoniummolybdate in 80 milliliters of distilled water. The alumina to beimpregnated was added to the solution and the resulting mixture wasallowed to stand overnight.

The impregnated alumina was dried subsequently under a heat lamp instatic air for a period of about 2 hours to remove the excess water. Thedried material was then calcined in static air at a temperature of1,000° F. for a period of 2 hours.

One-half of the calcined material was impregnated with a solution ofcobalt nitrate. This solution was prepared by dissolving 1.2 grams ofCo(NO₃)₂.6H₂ O in 40 milliliters of distilled water. The mixture ofcalcined material and solution was allowed to stand overnight.

The material was then dried under a heat lamp in static air for a periodof about 2 hours. The dried material was calcined in static air at atemperature of 1,000° F. for a period of 2 hours. The finished catalyst,Catalyst A, is a preferred embodiment of the catalyst that is employedin the process of the present invention. Its properties are listedhereinbelow in Table I.

EXAMPLE 2

A second catalyst, hereinafter identified as Catalyst B, was prepared tocontain 3.1 wt.% CoO, 8.1 wt.% MoO₃, and 8.1 wt.% Cr₂ O₃, based upon thetotal catalyst weight, on a Aero-100 alumina support. This catalyst wasprepared according to the preparation method discussed hereinabove inExample 1; however, the appropriate amounts of metals were utilized tofurnish the desired composition. This catalyst, Catalyst B, is anotherembodiment of the catalyst that is employed in the process of thepresent invention. Its properties are listed hereinbelow in Table I.

EXAMPLE 3

For comparative purposes, a catalyst, hereinafter identified as CatalystC, was prepared to contain 8.3 wt.% MoO₃ and 8.3 wt.% Cr₂ O₃, based uponthe total catalyst weight, on an Aero-100 alumina support. A 40.8-gramsample of Aero-100 alumina, obtained from the American Cyanamid Company,was impregnated with a solution containing ammonium dichromate andammonium molybdate. The Aero-100 alumina was in the form of14-to-20-mesh material and had been previously calcined at a temperatureof about 1,200° F. in air for a period of 2 hours.

The solution that was used for the impregnation was prepared bydissolving 6.8 grams of the ammonium dichromate and 5.3 grams of theammonium molybdate in 40 milliliters of distilled water.

The impregnated alumina was then dried under a heat lamp in static airovernight to remove the excess water. The dried material was thencalcined in static air at a temperature of 1,000° F. for a period of 2hours. The physical properties of this catalyst, Catalyst C, are listedhereinbelow in Table I.

EXAMPLE 4

For comparative purposes, a commercially-available catalyst was obtainedfrom the American Cyanamid Company. This commercial catalyst wasidentified as HDS-2A and was specified by the American Cyanamid Companyto contain 3 wt.% CoO and 13 wt.% MoO₃ on an alumina support. Thiscatalyst is identified hereinafter as Catalyst D and its physicalproperties are presented in Table I hereinbelow.

EXAMPLE 5

Another hydrotreating catalyst was employed for comparative purposes.This catalyst was obtained from the Nalco Chemical Company. Thecatalyst, identified hereinafter as Catalyst E, was specified to containabout 3.5 wt.% CoO and 12.5 wt.% MoO₃ on an alumina support. Itsproperties are presented hereinbelow in Table I.

                  TABLE I                                                         ______________________________________                                        CATALYST PROPERTIES                                                           CATALYST                                                                      HYDROGENATION                                                                 COMPONENT, WT. %  A      B      C    D    E                                   ______________________________________                                        CoO               1.1    3.1    --   3    3.5                                 Cr.sub.2 O.sub.3  8.2    8.1    8.3  --   --                                  MoO.sub.3         8.2    8.1    8.3  13   12.5                                PHYSICAL PROPERTIES                                                            SURFACE AREA, m.sup.2 /gm                                                                      176    186    208  330  284                                  PORE VOLUME, cc/gm                                                                              0.55   0.56   0.60                                                                               0.61                                                                               0.61                                AVG. PORE DIAM., A                                                                             125    120    116  73   86                                  % OF PORE VOLUME IN:                                                            0-50 A PORES    3.9    4.7    6.3  26.7 14.2                                  50-100 A PORES  66.3   65.4   69.5 58.8 76.3                                 100-150 A PORES  28.9   29.1   23.1 4.3  2.1                                  150-200 A PORES  0.3    0.3    0.4  1.6  0.8                                  200-300 A PORES  0.3    0.3    0.3  2.1  1.1                                  300-400 A PORES  0.1    0.1    0.1  0.8  0.8                                  400-600 A PORES  0.2    0.1    0.3  5.7  4.7                                 ______________________________________                                    

EXAMPLE 6

Each of the above-discussed catalyst was tested for its ability toconvert an Arabian light vacuum resid. Appropriate properties of thisfeedstock was presented hereinbelow in Table II.

                  TABLE II                                                        ______________________________________                                        FEED PROPERTIES                                                               ______________________________________                                        Carbon, wt. %            84.91                                                Hydrogen, wt. %          10.61                                                H/C (atomic)             1.499                                                Nitrogen, wt. %          0.34                                                 Sulfur, wt. %            4.07                                                 Nickle, ppm              17.5                                                 Vanadium                 51.1                                                 1,000° F. - fraction                                                                            13.6                                                 Ramsbottom carbon, wt. % 15.2                                                 Gravity, °API     8.8                                                  Asphaltenes, wt. %       8.0                                                  Oils, wt. %              39.2                                                 Resins, wt. %            52.8                                                 Resins/Asphaltenes       6.6                                                  ______________________________________                                    

Each test was carried out in a bench-scale test unit having automaticcontrols for pressure, flow of reactants, and temperature. The reactorwas made from 5/8-inch-inside-diameter stainless-steel, heavy-walledtubing. A 1/8-inch-outside-diameter thermowell extended up through thecenter of the reactor. The reactor was heated by an electrically-heatedsteel block. The hydrocarbon feedstock was fed to the unit by means of aRuska pump, a positive-displacement pump. The 14-to-20-mesh catalystmaterial was supported on 8-to-10-mesh alundum particles. Approximately20 cubic centimeters of catalyst were employed as the catalyst bed ineach test. This amount of catalyst provided a catalyst bed length ofabout 10 inches to about 12 inches. The 10-inch layer of 8-to-10-meshalundum particles was placed over the catalyst bed in the reactor foreach test. The catalyst that was employed was located in the annularspace between the thermowell and the internal wall of the3/8-inch-inside-diameter reactor.

Prior to its use, each catalyst was calcined in still air at atemperature of about 1,000° F. for 1 hour. It was subsequently cooled ina desiccator and loaded into the appropriate reactor.

The catalyst was then subjected to the following pretreatment. Thereactor was placed in the reactor block at a temperature of 300° F. Agas mixture containing 8 mole % hydrogen sulfide in hydrogen was passedover the catalyst at the rate of 1 standard cubic foot per hour (SCFH)at a pressure of 500 psig and a temperature of about 300° F. After 10 to15 minutes of such treatment, the temperature of the block was raised to400° F. After at least an additional 1 hour of time had elapsed and atleast 1 standard cubic foot of gas mixture had passed through thesystem, the temperature of the block was raised to 700° F. Then the gasmixture was passed through the catalyst bed for at least 1 additionalhour and in an amount of at least 1 standard cubic foot. At this point,the gas mixture was discontinued, hydrogen was introduced into the unitat a pressure of 1,200 psig, the flow of hydrogen was established at arate of about 0.6 SCFH, and the temperature was increased to provide anaverage catalyst bed temperature of 760° F. Subsequently, thehydrocarbon flow was established at a rate that would provide an LHSV of0.59 volume of hydrocarbon per hour per volume of catalyst. Effluentfrom the reaction zone was collected in a liquid product receiver, whilethe gas that was formed was passed through the product receiver to apressure control valve and then through a wet test meter to anappropriate vent.

After a period of from 1 to 3 days, the average catalyst bed temperaturewas increased to 780° F. After an additional amount of time, e.g., about3 to 5 days, the average catalyst bed temperature was increased to about800° F.

Selected samples were obtained from the product receiver and wereanalyzed for pertinent information. Results of the tests are presentedhereinbelow in Table III. These data were obtained from samples takenduring the fifth to ninth day of operation conducted at an LHSV of 0.59volume of hydrocarbon per hour per volume of catalyst, a temperature of800° F., and a pressure of 1,200 psig, unless otherwise indicated.

                  TABLE III                                                       ______________________________________                                        TEST RESULTS                                                                  RUN NO.           1      2      3    4    5                                   CATALYST          A      B      C    D    E                                   ______________________________________                                        OPERATING CONDITIONS                                                            TEMPERATURE, °F.                                                                       800    800    800  800  780                                   PRESSURE, psig  1,200  1,200  1,200                                                                              1,200                                                                              1,200                                 LHSV            0.59   0.59   0.59 0.59 0.59                                ______________________________________                                        HYDROGEN RATE                                                                 SCFB SAMPLE                                                                   FROM DAY          9      9      6    7    7-18                                ______________________________________                                        % SULFUR REMOVAL  75     83     65   77   85                                  % NICKEL REMOVAL  79     73     85   43   48                                  % VANADIUM REMOVAL                                                                              93     86     93   95   57                                  % ASPHALTENE                                                                  CONVERSION        79     75     70   69   54                                  % CONVERSION OF                                                               1,000° F. +                                                            MATERIAL          66     50     59   47   40                                  LIQUID GRAVITY, °API                                                                     20.9   20.7   20.1 19.9 20.4                                ______________________________________                                    

These results demonstrate that Run No. 1, which is a preferredembodiment of the process of the present invention and which employs apreferred embodiment of the catalyst that is employed in the process ofthe present invention, provides overall superior performance whencompared to the other test runs. It furnishes good desulfurization, goodnickel removal, superior vanadium removal, superior asphalteneconversion, and superior conversion of 1,000° F.+ material to 1,000° F.-material.

Run No. 2, which is another embodiment of the process of the presentinvention, employs a catalyst that contains more cobalt (3.1 wt.% CoO)than Catalyst A (1.1 wt.% CoO), but this larger amount still fallswithin the broad range of 0.1 wt.% to 5 wt.% CoO that is specifiedhereinabove for a catalyst that can be utilized in the process of thepresent invention. The increased amount of cobalt improves thedesulfurization activity, somewhat lowers the metals removal, asphalteneconversion, and conversion of the 1,000° F.+ material to 1,000° F.-material of the catalyst.

Run No. 3, which represents an embodiment of the process that is thesubject matter of and is claimed in co-pending application U.S. Ser. No.967,416, utilizes a catalyst that contains chromium and molybdenum, butnot cobalt, in its hydrogenating component. The absence of cobaltresults in less sulfur removal, slightly improved metals removal, lessasphaltene conversion, and less conversion of the 1,000° F.+ material.

Runs Nos. 4 and 5 represent comparative tests employing prior artcatalysts. These two runs provided essentially the same amount ofdesulfurization as that furnished by the process of the presentinvention. However, they gave poorer metals removal, asphalteneconversion, and conversion of 1,000° F.+ material to 1,000° F.-material.

In view of the above, the process of the present invention represents anew and novel process for hydrotreating heavy hydrocarbon streams. Theuse of a small amount of cobalt in the catalyst in conjunction with 2metals of Group VIB of the Periodic Table of Elements, namely, chromiumand molybdenum, unexpectedly makes the process utilizing that catalyst avery effective way to treat such heavy hydrocarbons.

What is claimed is:
 1. A process for hydrotreating a heavy hydrocarbonstream containing metals, asphaltenes, nitrogen compounds, and sulfurcompounds to reduce the contents of metals, asphaltenes, nitrogencompounds, and sulfur compounds in said stream, which process comprisescontacting said stream under suitable conditions and in the presence ofhydrogen with a catalyst comprising (1) the metals of molybdenum,chromium, and cobalt, (2) their oxides, (3) their sulfides, or (4)mixtures thereof on a large-pore, catalytically active alumina, saidmolybdenum being present in an amount within the range of about 5 wt.%to about 15 wt.%, calculated as MoO₃ and based upon the total catalystweight, said chromium being present in an amount within the range ofabout 5 wt.% to about 20 wt.%, calculated as Cr₂ O₃ and based upon thetotal catalyst weight, said cobalt being present in an amount within therange of about 0.1 wt.% to about 5 wt.%, calculated as CoO and basedupon the total catalyst weight, and said catalyst possessing a porevolume within the range of about 0.4 cc/gm to about 0.8 cc/gm, a surfacearea within the range of about 150 m² /gm to about 300 m² /gm, and anaverage pore diameter within the range of about 100 A to about 200 A. 2.The process of claim 1, wherein said catalyst is prepared by calcining apseudo-boehmite in static air at a temperature within the range of about800° F. to about 1,400° F. for a period of time within the range ofabout 1/2 hour to about 2 hours to produce a gamma-alumina andsubsequently impregnating said gamma-alumina with one or more aqueoussolutions of heat-decomposable compounds of said metals.
 3. The processof claim 1, wherein said catalyst contains molybdenum in an amountwithin the range of about 7 wt.% to about 13 wt.%, calculated as MoO₃and based upon the total catalyst weight, chromium in an amount withinthe range of about 6 wt.% to about 15 wt.%, calculated as Cr₂ O₃ andbased upon the total catalyst weight, and cobalt in an amount within therange of about 1 wt.% to about 3 wt.%, calculated as CoO and based uponthe total catalyst weight.
 4. The process of claim 1, wherein saidcatalyst has a pore volume within the range of about 0.5 cc/gm to about0.7 cc/gm, a surface area within the range of about 150 m² /gm to about250 m² /gm, and an average pore diameter within the range of about 110 Ato about 150 A.
 5. The process of claim 1, wherein said suitableconditions comprise a hydrogen partial pressure within the range ofabout 1,000 psia to about 3,000 psia, an average catalyst bedtemperature within the range of about 700° F. to about 820° F., an LHSVwithin the range of about 0.1 volume of hydrocarbon per hour per volumeof catalyst to about 3 volumes of hydrocarbon per hour per volume ofcatalyst, and a hydrogen recycle rate or hydrogen addition rate withinthe range of about 2,000 SCFB to about 15,000 SCFB.
 6. The process ofclaim 1, wherein said catalyst has about 0% to about 10% of its porevolume in pores having diameters that are smaller than 50 A, about 30%to about 80% of its pore volume in pores having diameters within therange of about 50 A to about 100 A, about 10% to about 50% of its porevolume in pores having diameters within the range of about 100 A toabout 150 A, and about 0% to about 10% of its pore volume in poreshaving diameters that are larger than 150 A.
 7. The process of claim 2,wherein the amount of molybdenum in said catalyst is within the range ofabout 7 wt.% to about 13 wt.%, calculated as MoO₃ and based upon thetotal catalyst weight, wherein the amount of chromium in said catalystis within the range of about 6 wt.% to about 15 wt.%, calculated as Cr₂O₃ and based upon the total catalyst weight, and wherein the amount ofcobalt in said catalyst is within the range of about 1 wt.% to about 3wt.%, calculated as CoO and based upon the total catalyst weight.
 8. Theprocess of claim 2, wherein said catalyst has a pore volume within therange of about 0.5 cc/gm to about 0.7 cc/gm, a surface area within therange of about 150 m² /gm to about 250 m² /gm, and an average porediameter within the range of about 110 A to about 150 A.
 9. The processof claim 2, wherein said suitable conditions comprise a hydrogen partialpressure within the range of about 1,000 psia to about 3,000 psia, anaverage catalyst bed temperature within the range of about 700° F. toabout 820° F., an LHSV within the range of about 0.1 volume ofhydrocarbon per hour per volume of catalyst to about 3 volumes ofhydrocarbon per hour per volume of catalyst, and a hydrogen recycle rateor hydrogen addition rate within the range of about 2,000 SCFB to about15,000 SCFB.
 10. The process of claim 2, wherein said catalyst has about0% to about 10% of its pore volume in pores having diameters that aresmaller than 50 A, about 30% to about 80% of its pore volume in poreshaving diameters within the range of about 50 A to about 100 A, about10% to about 50% of its pore volume in pores having diameters within therange of about 100 A to about 150 A, and about 0% to about 10% of itspore volume in pores having diameters that are larger than 150 A. 11.The process of claim 6, wherein the amount of molybdenum in saidcatalyst is within the range of about 7 wt.% to about 13 wt.%,calculated as MoO₃ and based upon the total catalyst weight, wherein theamount of chromium in said catalyst is within the range of about 6 wt.%to about 15 wt.%, calculated as Cr₂ O₃ and based upon the total catalystweight, and wherein the amount of cobalt in said catalyst is within therange of about 1 wt.% to about 3 wt.%, calculated as CoO and based uponthe total catalyst weight.
 12. The process of claim 6, wherein saidcatalyst has a pore volume within the range of about 0.5 cc/gm to about0.7 cc/gm, a surface area within the range of about 150 m² /gm to about250 m² /gm, and an average pore diameter within the range of about 110 Ato about 150 A.
 13. The process of claim 6, wherein said suitableconditions comprise a hydrogen partial pressure within the range ofabout 1,000 psia to about 3,000 psia, an average catalyst bedtemperature within the range of about 700° F. to about 820° F., an LHSVwithin the range of about 0.1 volume of hydrocarbon per hour per volumeof catalyst to about 3 volumes of hydrocarbon per hour per volume ofcatalyst, and a hydrogen recycle rate or hydrogen addition rate withinthe range of about 2,000 SCFB to about 15,000 SCFB.
 14. The process ofclaim 7, wherein said catalyst has a pore volume within the range ofabout 0.5 cc/gm to about 0.7 cc/gm, a surface area within the range ofabout 150 m² /gm to about 250 m² /gm, and an average pore diameterwithin the range of about 110 A to about 150 A.
 15. The process of claim7, wherein said suitable conditions comprise a hydrogen partial pressurewithin the range of about 1,000 psia to about 3,000 psia, an averagecatalyst bed temperature within the range of about 700° F. to about 820°F., an LHSV within the range of about 0.1 volume of hydrocarbon per hourper volume of catalyst to about 3 volumes of hydrocarbon per hour pervolume of catalyst, and a hydrogen recycle rate or hydrogen additionrate within the range of about 2,000 SCFB to about 15,000 SCFB.
 16. Theprocess of claim 7, wherein said catalyst has about 0% to about 10% ofits pore volume in pores having diameters that are smaller than 50 A,about 30% to about 80% of its pore volume in pores having diameterswithin the range of about 50 A to about 100 A, about 10% to about 50% ofits pore volume in pores having diameters within the range of about 100A to about 150 A, and about 0% to about 10% of its pore volume in poreshaving diameters that are larger than 150 A.
 17. The process of claim 8,wherein said suitable conditions comprise a hydrogen partial pressurewithin the range of about 1,000 psia to about 3,000 psia, an averagecatalyst bed temperature within the range of about 700° F. to about 820°F., an LHSV within the range of about 0.1 volume of hydrocarbon per hourper volume of catalyst to about 3 volumes of hydrocarbon per hour pervolume of catalyst, and a hydrogen recycle rate or hydrogen additionrate within the range of about 2,000 SCFB to about 15,000 SCFB.
 18. Theprocess of claim 8, wherein said catalyst has about 0% to about 10% ofits pore volume in pores having diameters that are smaller than 50 A,about 30% to about 80% of its pore volume in pores having diameterswithin the range of about 50 A to about 100 A, about 10% to about 50% ofits pore volume in pores having diameters within the range of about 100A to about 150 A, and about 0% to about 10% of its pore volume in poreshaving diameters that are larger than 150 A.
 19. The process of claim 9,wherein said catalyst has about 0% to about 10% of its pore volume inpores having diameters that are smaller than 50 A, about 30% to about80% of its pore volume in pores having diameters within the range ofabout 50 A to about 100 A, about 10% to about 50% of its pore volume inpores having diameters within the range of about 100 A to about 150 A,and about 0% to about 10% of its pore volume in pores having diametersthat are larger than 150 A.
 20. The process of claim 11, wherein saidcatalyst has a pore volume within the range of about 0.5 cc/gm to about0.7 cc/gm, a surface area within the range of about 150 m² /gm to about250 m² /gm, and an average pore diameter within the range of about 110 Ato about 150 A.
 21. The process of claim 11, wherein said suitableconditions comprise a hydrogen partial pressure within the range ofabout 1,000 psia to about 3,000 psia, an average catalyst bedtemperature within the range of about 700° F. to about 820° F., an LHSVwithin the range of about 0.1 volume of hydrocarbon per hour per volumeof catalyst to about 3 volumes of hydrocarbon per hour per volume ofcatalyst, and a hydrogen recycle rate or hydrogen addition rate withinthe range of about 2,000 SCFB to about 15,000 SCFB.
 22. The process ofclaim 12, wherein said suitable conditions comprise a hydrogen partialpressure within the range of about 1,000 psia to about 3,000 psia, anaverage catalyst bed temperature within the range of about 700° F. toabout 820° F., an LHSV within the range of about 0.1 volume ofhydrocarbon per hour per volume of catalyst to about 3 volumes ofhydrocarbon per hour per volume of catalyst, and a hydrogen recycle rateor hydrogen addition rate within the range of about 2,000 SCFB to about15,000 SCFB.
 23. The process of claim 14, wherein said suitableconditions comprise a hydrogen partial pressure within the range ofabout 1,000 psia to about 3,000 psia, an average catalyst bedtemperature within the range of about 700° F. to about 820° F., an LHSVwithin the range of about 0.1 volume of hydrocarbon per hour per volumeof catalyst to about 3 volumes of hydrocarbon per hour per volume ofcatalyst, and a hydrogen recycle rate or hydrogen addition rate withinthe range of about 2,000 SCFB to about 15,000 SCFB.
 24. The process ofclaim 15, wherein said catalyst has about 0% to about 10% of its porevolume in pores having diameters that are smaller than 50 A, about 30%to about 80% of its pore volume in pores having diameters within therange of about 50 A to about 100 A, about 10% to about 50% of its porevolume in pores having diameters within the range of about 100 A toabout 150 A, and about 0% to about 10% of its pore volume in poreshaving diameters that are larger than 150 A.
 25. The process of claim17, wherein said catalyst has about 0% to about 10% of its pore volumein pores having diameters that are smaller than 50 A, about 30% to about80% of its pore volume in pores having diameters within the range ofabout 50 A to about 100 A, about 10% to about 50% of its pore volume inpores having diameters within the range of about 100 A to about 150 A,and about 0% to about 10% of its pore volume in pores having diametersthat are larger than 150 A.
 26. The process of claim 20, wherein saidsuitable conditions comprise a hydrogen partial pressure within therange of about 1,000 psia to about 3,000 psia, an average catalyst bedtemperature within the range of about 700° F. to about 820° F., an LHSVwithin the range of about 0.1 volume of hydrocarbon per hour per volumeof catalyst to about 3 volumes of hydrocarbon per hour per volume ofcatalyst, and a hydrogen recycle rate or hydrogen addition rate withinthe range of about 2,000 SCFB to about 15,000 SCFB.
 27. The process ofclaim 23, wherein said catalyst has about 0% to about 10% of its porevolume in pores having diameters that are smaller than 50 A, about 30%to about 80% of its pore volume in pores having diameters within therange of about 50 A to about 100 A, about 10% to about 50% of its porevolume in pores having diameters within the range of about 100 A toabout 150 A, and about 0% to about 10% of its pore volume in poreshaving diameters that are larger than 150 A.